Manufacture of phosphine



United States Patent 3,387,934 MANUFACTURE OF PHOSPHINE Alfred 0. Minklei, Kenmore, N.Y., assignor to Hooker Chemical Corporation, Niagara Falls, N.Y., a corporation of New York No Drawing. Filed Oct. 12, 1964, Ser. No. 403,341 9 Claims. (Cl. 23-204) This invention relates to the preparation of phosphine. More particularly, it relates to a process for preparing phosphine by hydrolyzing an alkali metal amalgam that has been treated with phosphorus.

An object of the invention is to utilize an alkali metal amalgam for the preparation of phosphine.

Another object of the invention is to prepare phosphine chemically from an alkali metal amalgam and elemental phosphorus reaction mixture.

Further, an object of the invention is to prepare phosphine by a low temperature reaction.

In accordance with the invention, it has been found that phosphine may be prepared by contacting elemental phosphorus with an alkali metal amalgam to form a reaction product, and hydrolyzing the reaction product.

The alkali metal amalgam utilized in the process of the invention may be prepared by various methods. Examples of these methods are electrolysis of alkali metal salt solutions with a mercury cathode, mixing an alkali metal with mercury, displacement of alkali amalgams by another alkali metal salt, reaction of alkyl alkali metal compounds with mercury, and the reaction of mercury with a solution of alkali metal in liquid ammonia. All of the above preparations of an alkali metal amalgam are known in the art.

The alkali metals that may be employed in the practice of this invention are potassium, sodium, lithium, rubidium and cesium. The preferred alkali metal is sodium, used as the metal and in the form of its salts and compounds such as sodium chloride, sodium sulfate, sodium methoxide and sodium propoxide.

In a preferred embodiment of the invention, phosphorus is admixed with a liquid amalgam containing sodium. The mixture is then heated and, thereafter, hydrolyzed to evolve phosphine. Among the by-products formed, which remain behind in the reaction mixture are alkali metal salts and acids of phosphorus such as sodium phosphate, lithium phosphate, potassium hydrophosphate, phosphorous acid, hydrophosphorous acid and so forth.

The concentration of alkali metal in the amalgam may be varied. according to how the elemental phosphorus is to be added. It is preferred to add the phosphorus to a liquid amalgam at low temperatures, e.g., from about 40 to 90 degrees centigrade. As the heat required to form a liquid phase of an alkali metal amalgam varies with the concentration of alkali metal in mercury, the concentration of the alkali metal in the amalgam aifects the temperature utilized. It has been found that amalgams liquid at temperatures below about 90 degrees centigrade and having from 0.1 to about 80 percent by weight of an alkali metal give the better results. Amalgams containing from 0.1 to 1.5 and from about 20 to 80 percent by weight of an alkali metal are preferred. Other arnalgams in the range of about 1.5 to 20 percent by weight of an alkali metal are useful, but normally, temperatures above about 90 degrees centigrade are used to liquify such amalgams. Other concentrations will also result in useful reaction at temperatures from about 0 to 600* degrees centigrade. Phosphorus may also be added to a liquid amalgam maintained at a temperature of from 40 to about 300 degrees centigrade with the preferred temperature range being from about 40 to 90 degrees centigrade.

In the process of the invention, amalgams may also be used at superatmospheric pressure and subatmospheric pressures. Solid amalgams may be utilized, but it is preferred to utilize a liquid amalgam. An illustration of the invention is the utilization of a sodium amalgam cathode material of an electrolytic cell, preferably a cell for the electrolysis of an alkali metal chloride. This material may be Withdrawn from the cell periodically, treated with phosphorus, hydrolyzed, to recover phosphine, reprocessed to remove contaminants and circulated to the electrolytic cell for further use.

Phosphorus may be added to the amalgam under an inert condition, e.g., under a nitrogen atmosphere, or dissolved in a suitable solvent, or melted and added in a phosphorus carrier or vehicle such as tetrahydrofuran or toluene. Phosphorus may be dissolved in carbon disulfide, benzene, toluene, xylene, or other suitable solvent, and added to the amalgam. The formation of the amalgamphosphorus reaction product may be enhanced by heating the reaction mixture at temperatures in the range of about 25 to 100 degrees centigrade, preferably at about 40 to degrees centigrade. The reaction product is then hydrolyzed by known means to cause evolution of phosphine.

The amount of phosphorus added to the reaction mixture may vary with the metal added to or present in mercury. A molar weight ratio of alkali metal to phosphorus which may be utilized is from about 0.1:1 to 15:1, with the preferred ratio being between 0.4:1 and 7:1 and a more preferred ratio being in the range of from about 2:1 to 5:1. These ratios, of course, may be varied according to the alkali metal present in mercury to form the amalgam. For example, if sodium is the metal to be added to the mercury to form a sodium amalgam, the preferred ratio would be a 3:1 ratio of metal to phosphorus. However, greater or lesser amounts of sodium will also operate effectively. The time required to effect the reaction of phosphorus with the amalgam varies, but is usually in the range of 0.05 to 6 hours.

It is to be understood that various hydrolyzing agents may be utilized in the practice of this invention. Examples of hydrolyzing agents, include water, alcohols, which may be employed in aqueous solutions, aqueous inorganic hydrolyzing agents, and aqueous organic hydrolyzing agents, such as sulfuric acid, hydrochloric acid, sodium chloride, lithium chloride, potassium chloride, sodium sulfate, potassium sulfate, monosodium phosphate, disodium phosphate, methanol, hexanol, ethanol, heptanol, octadecanol, glycerine, glycols, e.g., ethylene glycol, and so forth. The amount of hydrolyzing agent employed may be from about 1 to 200 percent of the amount which releases as phosphine all the phosphorus of the reaction mixture capable of generating phosphine, but about the stoichiometric amount, with slight excess, when desired, from to percent hydrolyzing agent, based on the stoichiometric amount, is preferred. The rate at which the hydrolyzing agent is added to the phosphorus-containing amalgam may vary considerably. It may be desirable to add the hydrolyzing agent in an aqueous solution dropwise or in a steady stream. Either method has been found to be operable Within the instant invention.

The following examples are given to illustrate the present invention and are not to be taken as limitative. All temperatures are in degrees centigrade, and parts are by weight, unless otherwise specified.

Examples 1-15 In these examples, the reactants, conditions and results of which are set forth in Table I, the following procedure was followed. An alkali metal in the stated amount was added to the stated amount of mercury. Phosphorus (yellow) was added to this amalgam and heated, with stirring. After the reaction was completed, the reaction product was hydrolyzed. The phosphine evolved was collected under water and measured by absorbing an aliquot in sodium hypobromite.

TABLE I Variables: Reaction Temperature, degrees centigrade 77 77 78 68 68 Reaction Time,hours 2.6 2.3 2.4 2.9 1.8 Phosphorus Addition Time, l\iinutcs. 15 25 3 3 3 Rcactants:

Sodium, pnrts 3.02 3.02 2.55 5.0 Potassium, parts 3- 5.1 Phosphorus, parts 1.35 1.35 1.15 1.35 1.35 1.35 Tetrohydroturane, par 88. 3 88. 8 88. 8 133 133 Dioxane, parts Naphthalene, parts 5. 0 10 5.0 5.0 5.0 Benzophenone, parts 9.1 Mercury, parts 1,0 1,000 859 1,7 1,700 1,667 1,000 1,000 1, 000 1,000 1,000 1,000 Percent Amalgam. 0.3 0.3 0.3 0.170 0.3 0.3 .3 0.5 0.3 0,3 0,3 0,3 0,3 Dimethylether of diethyleue glycol, parts 150 r Products:

Phosphinc, parts 0.696 0.654 0.551 Sodium, parts 2.42 Hypophosphorus acid, parts- Phosphorus acid, parts- Yield, percent (phosphinc) 47 43 44 46. 6 37.2 47. 43 36.2 42.0 40 41 49 49 40 41 i From Phosphorus Addition.

2 Added at once into reactor.

In Examples 1, 2 and 3, phosphorus was dissolved in 86.6 parts of toluene and added to the amalgam while in all the other examples phosphorus was melted and added under tetrahydrofuran or toluene. The tetrahydrofuran concentrations in Examples 4, 5 and 6 were varied. The results obtained evidenced slight improvement on an in crease of solvent. Dioxane was utilized as a medium for phosphorus in Example 7, while the dimethyl ether diethylene glycol was utilized as a phosphorus medium in Example 8.

Various sodium carriers, such as naphthalene and benzophenone (see Examples 1, 2 and 9), were successfully utilized. In Examples 4 and 5, potassium was utilized in lieu of sodium.

In Examples and 11, the sodium carrier was eliminated, except for a small amount of solvent (8.9 parts of tetrahydrofuran) in which phosphorus was melted. In the presence of a small amount of phosphorus solvent there was no difference in phosphine production.

In Example 12, elemental phosphorus was dropped directly onto the amalgam held under a nitrogen atmosphere. Phosphine was successfully recovered.

Examples 13 and 14 were run in accordance with the previous examples, but operating at temperatures of 44 and 135 degrees centigrade, respectively.

Example illustrates residual amounts of various phosphorus compounds not evolved as phosphine.

In Examples 12 and 14, 80 percent aqueous ethanol was used as the hydrolyzing agent; in Example 15, dilute hydrochloric acid was used; in the remaining examples Water was used as the hydrolyzing agent, the hydrolyzing agents being used in a percent stoichiometric excess.

In view of the above examples and the rapid evolution of phosphine on hydrolysis of the amalgam phosphorus reaction product it appears that an alkali metal phosphide is formed on addition of phosphorus to amalgam which is hydrolyzed to yield phosphine.

While there have been described various embodiments of the invention, the compositions and methods described are not intended to be limitative of the scope of the invention, so it is realized that changes therein and substitution of equivalents are possible. It is further intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same results in substantially the same or equivalent manner, the claims covering the invention broadly in Whatever form its principle may be utilized.

What is claimed is:

1. A process comprising reacting elemental phosphorus with an alkali metal amalgam at a temperature from 0 degrees centigrade in the absence of a hydrolyzing agent to 600 degrees centigrade, said reacting being sufiicient to form an alkali metal phosphide, and thereafter adding a hydrolyzing agent to said alkali metal phosphide in an amount sufiicient to hydrolyze said phosphide and thereby producing phosphine.

2. A process in accordance with claim 1 wherein the alkali metal amalgam used is that obtained from a mercury cell for the electrolysis of alkali metal chlorides.

3. A process in accordance with claim 1 wherein the amalgam is in liquid form at 40 to about 300 degrees centigrade.

4. A process according to claim 3, in which said alkali metal amalgam contains from 0.1 to 10 weight percent alkali metal in an amount equal to a mole ratio of 0.111 to 15:1 alkali metal to phosphorus.

5. A process according to claim 1, in which said alkali metal amalgam is sodium amalgam and contains from 0.1 to 10 percent :by weight of alkali metal in said amalgam, and in which said phosphorus is yellow phosphorus.

6. The method of claim 5 wherein the phosphorus is dissolved in a solvent prior to adding to the amalgam.

7. The method of claim 5 wherein the phosphorus is melted and added to the amalgam under a solvent.

8. A process comprising in the absence of a hydrolyzing agent adding yellow phosphorus in a solvent to a liquid sodium-amalgam containing 0.1 to 5 percent sodium equal in a ratio of 0.1:1 to 5:l sodium to phosphorus, sufficient to form a reaction mixture in the absence of a hydrolyzing agent, and reacting said reaction mixture at from 40 degrees centigrade to about 90 degrees centigrade for 0.05 to 6 hours, sufliciently to produce sodium phosphide, and subsequently hydrolyzing said sodium phosphide sufficiently to evolve phosphine.

9. A process comprising reacting elemental phosphorus with an alkali metal amalgam liquid at less than 90 degrees centigrade, said reaction temperature being from 40 degrees centigrade to 90 degrees centigrade, said amalgam including from 0.1 to percent alkali metal, said phosphorus being reacted in an amount from 0.1:1 to 5 :l alkali metal to phosphorus, said reacting being sufficient to form an alkali metal phosphide, and said reacting being in the absence of a hydrolyzing agent.

OTHER REFERENCES Mellor: Comprehensive Treatise on Inorganic and Theoretical Chemistry, vol. 8, pp. 804805, 1928.

EARL C. THOMAS, Primary Examiner.

OSCAR R. VERTIZ, Examiner.

H. S. MILLER, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,387,934 June 11, 1968 Alfred O. Minklei It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below: Column 1, line 45, "hydrophosphate should read pypophosphate line 46, hydrophosphorus should read hypophosphorus Signed and sealed this 31st day of March 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR

Edward M. Fletcher, 11'.

Commissioner of Patents Attesting Officer 

1. A PROCESS COMPRISING REACTING ELEMENTAL PHOSPHORUS WITH AN ALKALI METAL AMALGAM AT A TEMPERATURE FROM 0 DEGREES CENTIGRADE IN THE ABSENCE OF A HYDROLYZING AGENT TO 600 DEGREES CENTIGRADE, SAID REACTING BEING SUFFICIENT TO FORM AN ALKALI METAL PHOSPHIDE, AND THEREAFTER ADDING A HYDROLYZING AGENT TO SAID ALKALI METAL PHOSPHIDE IN AN AMOUNT SUFFICIENT TO HYDROLYZE SAID PHOSPHIDE AND THEREBY PRODUCING PHOSPHINE. 